Servicing Mission 2

After a successful first mission to correct Hubble’s vision in 1993, a second Servicing Mission (STS-82) was launched to the space telescope in February 1997. The goal of this 10-day operation was to enhance Hubble’s scientific capabilities for discovery by conducting a number of maintenance tasks and refurbishing the existing systems.

STS-82 included the installation of two technologically advanced instruments by a crew of astronauts who reached Hubble aboard the Discovery Space Shuttle. Both devices featured technology that was not available when the first designs of the Hubble Space Telescope were produced.

The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Space Telescope Imaging Spectrograph (STIS) replaced the Faint Object Spectrograph (FOS) and the Goddard High Resolution Spectrograph (GHRS) respectively.

NICMOS has enabled astronomers to dig into the nature of dusty galactic centres and to gain valuable knowledge of star and planet formation. Consisting of three cameras, NICMOS has proven effective at providing infrared and spectroscopic observations of cosmological objects. One of NICMOS’s key contributions is having presented the world with the first image of our Universe at near-infrared wavelengths. These wavelengths are not observable to the human eye, but allow us to probe the distant Universe. Endowed with powerful detectors, NICMOS has been able to offer views of our Universe that no other previous optical or ultraviolet device has ever been capable of.

STIS is a powerful spectroscopic device sensitive to light in ultraviolet wavelengths. It employs two-dimensional detectors that gather 30 times more spectral data and 500 times more spatial data than the first generation Hubble spectrographs. STIS is considered to be the most complex scientific instrument built for space science. With its high sensitivity and resolution, scientists have studied the distribution of mass across the Universe, star formation in faraway galaxies, and supermassive blackholes.

Fine Guidance Sensors (FGS). These optical sensors are part of Hubble’s Pointing Control System. As such, they keep Hubble steady while observing objects. Refurbishing the FGS has allowed for alignment corrections from the Earth. They are also employed by scientists to calculate celestial distances.

Optical Control Electronics Enhancement Kit (OCE-EK). Used to adjust the Fine Guidance Sensors (FGS), which keep the telescope still and aligned, ensuring that the science instruments produce sharp images.

A new type of Solid State Recorder (SSR) replaced one of Hubble’s three Engineering Science Tape Recorders (ESTR). SSR is a state-of-the-art digital recorder that stores significantly more data than the old reel-to-reel recorder.

Astronauts also replaced one of Hubble’s four Reaction Wheel Assemblies (RWA). This device consists of a set of wheels that moves the telescope from target to target. As such, it is also part of Hubble’s Pointing Control System.

Replacement of one of Hubble’s two sets of Solar Array Drive Electronics (SADE) was also conducted. Such modular hardware controls the position of the solar arrays and is provided by the European Space Agency, NASA’s partner in the Hubble project.

One of the telescope’s four Data Interface Units (DIU) was replaced with an upgraded version. These units receive and send commands and data requests between the telescope’s management system and the other subsystems.

A tape recorder that stores up to one billion bits of science and engineering data but that cannot be transmitted to the ground in real time was also installed.

New Magnetic Sensing System Covers were installed. They enclosed the device responsible for measuring the telescope’s orientation relative to the Earth’s magnetic field.